1. Field of the Invention
The present invention relates to an air conditioner for vehicle use in which the blowing air temperature is adjusted when a ratio of the volume of a cold air to the volume of a hot air is adjusted.
2. Description of the Related Art
Concerning the blowing air temperature adjusting system provided in an air conditioner for vehicle use, in a typical system, the air mixing type temperature adjusting system adjusts a ratio of the volume of a cold air to the volume of a hot air so as to adjust the blowing air temperature.
Concerning the air mixing door which is a temperature adjusting means in this air mixing type air temperature adjusting system, a plate door type and a film door type air mixing door are well known.
FIG. 8A is a view showing a case in which the air mixing door is composed of a plate door. When the air mixing door 30, composed of a one piece plate door, is rotated round the rotary shat 31, the area of the cold air passage 6, which bypasses the heater core 5, and the area of the hot air passage 7, which is provided on the heater core 5 side, are adjusted so as to adjust a ratio of the volume of a cold air to the volume of a hot air.
In this connection, in FIG. 8A, the broken line position 30a of the air mixing door 30 is the maximum cooling position at which the cold air passage 6 is fully opened and the hot air passage 7 is fully closed, and the one-dotted chain line position 30b is the maximum heating position at which the hot air passage 7 is fully opened and the cold air passage is fully closed.
FIG. 9A is a view showing a case in which the air mixing door 40 is composed of a film door which is made of a flexible thin film member 40a. As shown in FIG. 9B, the opening 40b, in which air passes through, is provided on the thin film member 40a. The upper and the lower end portion of the thin film member 40a are connected to the winding shafts 41, 42. When both the winding shafts 41, 42 are rotated being interlocked with each other, the upper and the lower end portion of the thin film member 40a are wound round the winding shafts 41, 42. Alternatively, the upper and the lower end portion of the thin film member 40a are sent out (rewound) from the winding shafts 41, 42. The intermediate portion of the thin film member 40a is guided by the intermediate guide portion 43.
When both the winding shafts 41, 42 are rotated, the thin film member 40a moves across the cold air passage 6 and the hot air passage 7. Therefore, an overlapping position, at which the opening 40b of the thin film member 40a overlaps the cold air passage 6 and the hot air passage 7, is changed, so that the passage (opening) areas of the cold air passage 6 and the hot air passage 7 can be adjusted.
In the former case of the air mixing door 30 composed of the plate door, it is necessary to provide an operation space, in which the plate door is rotated, in the case 2. Therefore, it is disadvantageous that the dimensions of the case 2 are increased.
Further, the following problems may be encountered. When the air mixing door 30 is rotated from the maximum cooling position 30a to the intermediate temperature controlling position (shown by the solid line), the hot air passage 7 in the rotary direction of the plate door is opened, and at the same time, the passages (the passages in the perpendicular direction to the surface of FIG. 8A) on the right and the left of the plate door are opened. Therefore, the area of the hot air passage 7 is suddenly increased.
When the air mixing door 30 is rotated from the maximum heating position 30b to the intermediate temperature controlling position (the solid line position), the cold air passage 7 in the plate door rotating direction is opened, and at the same time, the passages on the right and the left (the passages perpendicular to the surface of FIG. 8A) of the plate door are opened. Therefore, the area of the cold air passage 6 is suddenly increased.
On the other hand, when the air mixing door 30 is operated at the intermediate temperature controlling position exemplarily shown by the solid line in the view, as the right plate door passage and the left plate door passage (shown by the solid line) of the cold air passage 6 and the hot air passage 7 have already been opened, the areas of the cold air passage 6 and the hot air passage 7 are gradually changed with respect to the change in the rotary angle of the plate door.
As a result, the control characteristic of controlling the blowing air temperature by the air mixing door composed of the plate door is deteriorated as shown in FIG. 8B. The axis of abscissa of FIG. 8B represents a rotary angle of the air mixing door 30. The rotary angle at the maximum cooling position 30a is set at 0°, and the rotary angle at the maximum heating position 30b is set at the maximum angle θ.
As shown in FIG. 8B, the following characteristic is provided. The blowing air temperature is suddenly changed with respect to the rotary angle of the air mixing door 30 in the regions (1) and (2) in the neighborhoods of the maximum cooling position 30a and the maximum heating position 30b. Further, the blowing air temperature is gradually changed in the intermediate temperature control region (3). Therefore, in the region (1) in the neighborhood of the maximum cooling region 30a and in the region (2) in the neighborhood of the maximum heating region 30b, it becomes difficult to control the blowing air temperature.
On the other hand, in the latter case of the air mixing door 40 composed of a film door, the following advantages can be provided. As the thin film member 40a moves across the cold air passage 6 and the hot air passage 7, it is unnecessary to provide a rotary operation space, which is different from the case in which the plate door is used. Therefore, the dimensions of the case 2 can be reduced.
Further, as a current of air always flows in the cold air passage 6 and the hot air passage 7 passing through only in the opening 40b provided on the thin film member 40a, the areas of the cold air passage 6 and the hot air passage 7 can be changed by a predetermined ratio with respect to the change in the moving position of the thin film member 40a. Therefore, the blowing air temperature can be substantially linearly adjusted by the change in the position of the opening 40b of the thin film member 40a over all the region between the maximum cooling state to the maximum heating state. Accordingly, the air mixing door 40 composed of the film door is advantageous in that the blowing air temperature control characteristic can be improved as compared with the case in which the plate door is used.
In this connection, in FIG. 9C, “O” on the axis of abscissa represents the maximum cooling position at which the opening 40b on the thin film member 40a overlaps the cold air passage 6 so that the cold air passage 6 can be fully opened, and at the same time the film portion of the thin film member 40a overlaps the hot air passage 7 so that the hot air passage 7 can be fully closed. In FIG. 9C, “L” on the axis of abscissa represents the maximum heating position at which the opening 40b of the thin film member 40a overlaps the hot air passage 7 so that the hot air passage 7 can be fully opened, and at the same time the film portion of the thin film member 40a overlaps the cold air passage 6 so that the cold air passage 6 can be fully closed.
However, as the opening 40b, the area of which is predetermined, which is provided on the thin film member 40a composing the film door, is moved and the passage areas of the cold air passage 6 and the hot air passage 7 are adjusted by the opening 40b, when the opening 40b on the thin film member 40a is moved to the intermediate temperature control position between the maximum cooling position and the maximum heating position as shown in FIG. 9A and the blowing air temperature is adjusted at a value in the intermediate temperature region close to 25° C., the passage area in the case 2 is necessarily restricted by the opening area of the opening 40b. 
In the case where the air mixing door 30 composed of the plate door is used, a current of air flows in the cold air passage 6 and the hot air passage 7 at all times. Therefore, it is possible to reduce a pressure loss of draft generated in the case 2. However, in the case where the air mixing door 40 composed of the film door is used, the passage area in the case 2 is restricted by the opening area of the opening 40b at all times. Therefore, the pressure loss of draft is increased.
For the above reasons, the pressure loss generated in the air passage in the intermediate temperature region, which is most frequently used through the year, becomes larger than that of the plate door type. Accordingly, noise is increased in the operation of the blower and further the electric power consumption of the blower is increased.